Dynamics and control of a parallel-plates reactor for ethanol steam reforming thermally coupled with catalytic ethanol combustion

Abstract

This paper examines the design and dynamics of a compact heat-integrated parallel-plates milli-reactor for hydrogen production via ethanol steam reforming, thermally integrated with ethanol combustion. Catalysts are washcoated on metal structures separated by metal sheets. The reactor’s non-steady state is rigorously modeled to identify control system variables. Temperature and flowrate disturbances affect the outlet temperature, molar composition, and hydrogen yield. The mass response is almost instantaneous, while the thermal response takes about 300 seconds to stabilize. Adjusting the flowrate to the reforming section accommodates changes in H2 demand. The ethanol feed to the combustion section is optimal for manipulating syn-gas temperature and composition. The closed-loop study employs four control modes. Process stability is tested with set-point changes of ±35 °C, showing that the reactor remains stable across all control modes. The model’s non-linearity is evident from the varied response. P and PD controllers ensure stability and rapid steady-state achievement but have an offset of ±14 °C due to the lack of integral action. For ±30 % changes in reforming flowrate, the control system handles disturbances with a ±12 °C offset under P and PD controllers, and no offset under PI and PID controllers, maintaining system stability throughout.